We propose to develop a long term mammalian hepatocyte tissue culture model that offers the following unique features: (1) Perfused medium exchange via a capillary system that; (2) allows continuous, precise monitoring and adjustment of oxygen, nutrient, and cell product levels; (3) with a high degree of cell-cell contact. As steps in developing this model we will: (1) Characterize ultrastructural changes in hepatocytes from the in vivo state, through the isolation procedure and into culture, (2) ascertain the optimum conditions for hepatocyte attachment to the artificial membrane surfaces, (3) determine oxygen demand by hepatocytes in perfusion culture, and (4) determine optimal nutrient and hormone levels in perfusion culture. Leakage of lactate dehydrogenase will be used as a gross indication of hepatocyte condition to make initial culture condition adjustments. Assay of several hepatocyte functions, including albumin synthesis, organic anion dyes, drug metabolism, and bile acid conjugation will be used to make final modifications to the system so that differentiated liver function is maintained over longer periods of time than is possible with existing hepatocyte monolayer culture models. Our model will be useful for studies of normal differentiated liver functions and of pathological liver conditions.